Licurg: Still doesn't work.
Did you change/update anything between when the game was working and when it started giving that error?
Are you shutting down all non-essential programs (especially anti-virus) before starting the game? Firewalls have also caused problems on startup, but not that error, that I've seen reported before.
Try starting the game directly from the '..\Divinity - Original Sin\Shipping\EoCApp.exe' program file, by right clicking and running as administrator. Also, you could try right clicking, selecting Properties and switching to the Compatibility tab (default shortcut for me in Win 7 64 has run as administrator and disable display scaling on high DPI settings checked).
Try browsing to the '..\Documents\Larian Studios' folder and renaming the 'Divinity Original Sin' subfolder.
This folder contains the saved games, configuration files and a level cache folder. The game should recreate it on startup the next time it is run (aside from the saves and the DLC subfolder, which the GOG version uses to keep track of the companion and (if applicable) Source Hunter DLC).
If that lets you start the game and create a new profile, exit, maybe reboot and make sure you can restart the game. If so, move the saves from the renamed folder into the new profile's savegames folder, and move the DLC folder to the new D:OS folder.